1. Field of the Invention
The present invention relates to an imaging device and an image forming apparatus of electrophotographic type, and particularly relates to an imaging device including a charging unit and a lubricant applying unit for applying a lubricant on an image carrying member and relates to an image forming apparatus including that imaging device.
2. Description of the Related Art
In imaging devices used in electrophotographic image forming apparatuses, it is known that the discharge produced by a charging unit leads to the generation of discharge products such as ozone or nitrogen oxide (NOx). Besides, with regard to recent image forming apparatuses, the demand for large-quantity printing has been on the rise. In order to meet that demand, development of high-speed image forming apparatuses is well underway. With the aim of achieving a high speed, charging chargers that are compatible to high speed processing are being preferred over charging rollers. However, the use of such charging chargers leads to an increase in the generated quantity of discharge products.
In image forming apparatuses including a charging charger, an air duct is disposed to form an airstream path through which the discharge products generated from the charging charger are removed from the vicinity thereof. Moreover, an ozone filter is disposed at the duct outlet so that the discharge products are filtered before being let to pass to the outside of the image forming apparatus.
Hence, usually, the discharge products do not remain inside the image forming apparatus. However, if problems such as clogging of the ozone filter, decline in the room ventilation capacity, or deterioration of the charging charger lead to the generation of a large quantity of discharge products that exceeds the filtering capacity of the ozone filter, then it becomes difficult to sufficiently evacuate the discharge products. Thus, sometimes the discharge products remain in the vicinity of the charging charger. If an image forming job is performed when the discharge products remain attached to the image carrying member, then electrostatic latent images get distorted and the image development also gets affected. As a result, the output images become blurred (hereinafter, “blurred images”).
To address such an issue, Japanese Patent Application Laid-open No. 2008-96518 discloses a technology as follows: upon completion of an image forming job, a post-image-formation lubricant applying mode is implemented in which a photosensitive body functioning as the image carrying member is rotated and a lubricant applying device is operated in such a way that a thicker adhering layer of lubricant is formed on the photosensitive member after the image forming job is complete. Hence, even if the discharge products are attached to the photosensitive member, they can be removed along with the adhering layer of lubricant by a cleaning unit prior to the start of the subsequent image forming job. Such measures prevent the formation of blurred images.
However, in a configuration in which an adhering layer of lubricant is formed on a photosensitive drum as disclosed in Japanese Patent Application Laid-open No. 2008-96518, the adhering layer of lubricant undergoes deterioration if the image forming apparatus is left unattended for a long period of time such as during the night-time. In such a case, the adhering layer of lubricant having the discharge products adsorbed therein gets so firmly attached to the photosensitive member that the cleaning unit cannot easily remove the adhering layer of lubricant prior to the start of the subsequent image forming job. That makes it harder to perform correction of blurred images. In order to eliminate the blurred images, an idle operation mode such as the post-image-formation lubricant applying mode needs to be implemented for a plurality of times prior to the start of the subsequent image forming job.